A vehicle powertrain typically includes a transmission, an engine, and a powertrain controller. The transmission transfers engine output torque through a gear reduction to a driveshaft, which rotates the wheels of the vehicle. The powertrain controller controls the operation of the transmission and the engine. Powertrains traditionally include launch devices including, but not limited to, a torque converter or friction clutch. More specifically, automatic transmissions generally include a torque converter and manual or automated manual transmissions (AMTs) include a friction clutch. Friction launch devices gradually couple rotating members so that they become fixed for rotation together.
Traditional friction launch control strategies include closed loop slip speed control and fluid coupling emulation control. Closed loop slip speed control monitors the slip speed across the friction launch device and regulates the slip speed so that is follows a single, desired profile. Closed loop slip speed control is not sufficiently robust against system variations and can not maintain stable operation. Fluid coupling emulation control simulates fluid coupling characteristics and regulates the friction launch device to emulate a single torque absorption curve. Fluid coupling emulation control, however, does not provide sufficient degrees of freedom to achieve a desired engine stall speed for a variety of throttle openings.